A variety of medical conditions are treated by introducing an insertable or implantable medical device into the body. In some instances, exposure to a medical device which is implanted or inserted into the body of a patient can cause the body tissue to exhibit adverse physiological reactions. For example, the insertion or implantation of certain catheters or stents can lead to the formation of emboli or clots in blood vessels. Similarly, the implantation of urinary catheters can cause infections, particularly in the urinary tract. Other adverse reactions to medical devices include, without limitation, cell proliferation which can lead to hyperplasia, occlusion of blood vessels, platelet aggregation, rejection of artificial organs, and calcification.
In order to address such adverse effects, medical devices have included therapeutic agents. Such materials can be incorporated into the materials used to make the device. Alternatively, the therapeutic agents can be included in a coating that is applied to a surface of the medical device.
Moreover, medical devices that include a therapeutic agent can be used for direct or local administration of the therapeutic agent to a particular part of the patient's body. For instance, stents having coatings that include a therapeutic agent can be used to treat or prevent restenosis. In some instances, the coating can also include a polymeric material that affects the delivery or release of the therapeutic agent. For example, various types of coated stents in which the coating includes a therapeutic agent have been used for localized delivery of such therapeutic agent to a body lumen. See, e.g., U.S. Pat. No. 6,099,562 to Ding et al. Such direct or local administration may be more preferred than systemic administration of a therapeutic agent. Systemic administration requires larger amounts and/or higher concentrations of the therapeutic agent because of indirect delivery of such agents to the afflicted area. Also, systemic administration may cause side effects which may not be a problem when the therapeutic agent is locally administered.
Given the advantages of medical devices having coatings that include a therapeutic agent, there exists a need for such coated medical devices, particularly medical devices that have a coating comprising a therapeutic agent and a polymer. Of particular interest are medical device coatings that can control the delivery and release kinetics or profile of a therapeutic agent from the coating and that can be fabricated with minimal efforts. For example, improving the controlled release of the therapeutic agent can be achieved by coating the medical device and then damaging the coating by creating holes, slits, etc. in the coating. Such damage to the coating can affect the release of the therapeutic agent by affecting the effective surface area from which the therapeutic agent can be released from the coating. Nevertheless there exists a need for medical device coatings in which the release profile of a therapeutic agent can be controlled or modified.